Seroprevalence and risk factors for Toxoplasma gondii transmission in wild, domestic and companion animals in urban informal settlements from Salvador, Brazil

Bazan, L.; Argibay, H. D.; Borges-Silva, W.; Pita Gondim, L. F.; dos Santos Mattos, T. A.; Oliveira Santana, J.; Mendes da Silva, E.; Begon, M.; Khalil, H.; Costa, F.; de Oliveira Carneiro, I.

doi:10.1101/2025.07.01.662552

bioRxiv · 10.1101/2025.07.01.662552

Seroprevalence and risk factors for Toxoplasma gondii transmission in wild, domestic and companion animals in urban informal settlements from Salvador, Brazil

Bazan, L.·Argibay, H. D.·Borges-Silva, W.·Pita Gondim, L. F.·dos Santos Mattos, T. A.·Oliveira Santana, J.·Mendes da Silva, E.·Begon, M.·Khalil, H.·Costa, F.·de Oliveira Carneiro, I.

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Abstract

Toxoplasma gondii is a globally neglected zoonotic parasite, particularly prevalent in socioeconomically vulnerable areas. Various animal species serve as reservoirs for T. gondii across different regions, including domestic cats, livestock, and a variety of wild and synanthropic animals. In urban areas, especially informal settlements, the close coexistence of humans, domestic animals, and wildlife may influence local transmission dynamics. This study evaluated the seroprevalence and associated risk factors for T. gondii infection in domestic and synanthropic animals from two low-income communities in Salvador, Brazil. A cross-sectional study was conducted in the neighborhoods of Marechal Rondon and Pau da Lima from October 2021 to February 2023. Blood samples were collected from domestic animals (288 dogs, 112 cats, 27 chickens, and six horses) and synanthropic species (54 brown rats and 75 big-eared opossums). Serological tests were performed using an indirect immunofluorescence antibody test. Questionnaires were used to collect environmental, demographic, and socioeconomic data from households where sampling took place. Generalized linear mixed models were applied to identify predictors of exposure. Seroprevalence was highest in chickens (66.7%), followed by dogs (37.2%), rats (24.1%), cats (22.3%), opossums (20%), and horses (16.7%). No significant factors were found to be associated with T. gondii seroprevalence in chickens, horses, rats, or opossums. Nevertheless, in dogs and cats, homemade diets increased the odds of infection by nearly six times compared to commercial feeding. Dogs from Pau da Lima were twice as likely to be infected as those from Marechal Rondon. These findings underscore the importance of promoting safe pet management, improving sanitation, and monitoring sentinel species to mitigate zoonotic risks in urban informal settlements. Author summaryToxoplasma gondii is a parasite that infects humans and animals worldwide, significantly impacting impoverished areas. In this study, we investigated the prevalence and factors associated with T. gondii infection in domestic and urban wildlife from two low-income communities in Salvador (BA, Brazil). We collected blood samples from dogs, cats, chickens, horses, rats, and opossums to test for antibodies against the parasite and analyzed environmental and lifestyle factors that might influence infection risk. Chickens showed the highest infection rates (67%), followed by dogs (37%), rats (24%), cats (22%), opossums (20%), and horses (17%). We found that homemade diets significantly increased the likelihood of infection in dogs and cats compared to commercial pet food. Additionally, dogs from one neighborhood were twice as likely to be infected as those from the other, likely due to environmental conditions. These findings highlight how diet, environment, and urban living conditions affect the spread of T. gondii. By improving sanitation, promoting responsible pet care, and monitoring animals that share human environments, we can reduce the risk of this parasite in vulnerable communities.

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Bazan, L., Argibay, H. D., Borges-Silva, W., Pita Gondim, L. F., dos Santos Mattos, T. A., Oliveira Santana, J., Mendes da Silva, E., Begon, M., Khalil, H., Costa, F., de Oliveira Carneiro, I.. 2025-07-07. Seroprevalence and risk factors for Toxoplasma gondii transmission in wild, domestic and companion animals in urban informal settlements from Salvador, Brazil. https://doi.org/10.1101/2025.07.01.662552

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